Compositions having isocyanate functional components are utilized to bond substrates together, such as, glass, often in the form of windows, into structures. In automotive assembly plants windows are often bonded in with one part adhesive compositions containing isocyanate functional components, which cure by reaction with ambient moisture, and take several hours or days to cure. In the assembly plants, vehicles are not driven for several hours and this is acceptable. One part moisture curing adhesives known in the art are disclosed in U.S. Pat. Nos. 4,374,237; 4,687,533; 4,780,520; 5,063,269; 5,623,044; 5,603,798; 5,852,137; 5,922,809; 5,976,305; 5,852,137 and 6,512,033, relevant portions incorporated herein by reference.
Two-part compositions containing isocyanate functional prepolymers in one part and compounds having isocyanate reactive components in the other part are used where cure speed is important, such as in the automotive aftermarket replacement glass business. Customers desire that the adhesives cure quickly so that the vehicle can be driven as soon as possible after replacing the window. Examples of two-part compositions are disclosed in EP 1,524,282, U.S. Pat. Nos. 5,852,103; 6,709,539; 7,101,950 and 7,361,292, incorporated herein by reference in its entirety. For certain applications even two part compositions containing isocyanate functional prepolymers do not cure fast enough for certain applications or customers. One solution previously utilized commercially involved contacting an isocyanate functional prepolymer with a paste containing water, see Hsieh et al U.S. Pat. No. 4,687,533 incorporated herein by reference in its entirety. For Original Equipment Manufacturing, the use of two part systems has been replaced with one part systems containing catalysts that facilitate fast curing, see for example Risk et al. U.S. Pat. No. 4,780,520, incorporated herein by reference in its entirety. Some skilled artisans have attempted to address this problem by increasing catalyst concentrations or other formulation adjustments, many of these formulation adjustments result it formation of bubbles in the adhesive. Bubbles in the cured adhesive can result in dramatic reduction in the strength of the cured adhesives. These adhesives can be used in applications that are safety related and such reductions in strength are unacceptable.
The cure rate of adhesive systems with fast curing catalysts can be slower than desired when temperatures are significantly below ambient temperatures (about 23° C.) and/or ambient relative humidity's are low (less than 50 percent RH). There is a need for even faster curing systems when temperatures and/or relative humidity's are low. Thus, what are needed are adhesive systems which exhibit rapid cure rates at low ambient temperatures and humidity's and which do not form bubbles in the cured adhesives.